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db807e5ef8
When xdp is attached or detached, dev->ndo_bpf() is called by
do_setlink(), and it acquires netdev_lock() if needed.
Unlike other drivers, the bnxt driver is protected by netdev_lock while
xdp is attached/detached because it sets dev->request_ops_lock to true.
So, the bnxt_xdp(), that is callback of ->ndo_bpf should not acquire
netdev_lock().
But the xdp_features_{set | clear}_redirect_target() was changed to
acquire netdev_lock() internally.
It causes a deadlock.
To fix this problem, bnxt driver should use
xdp_features_{set | clear}_redirect_target_locked() instead.
Splat looks like:
============================================
WARNING: possible recursive locking detected
6.15.0-rc6+ #1 Not tainted
--------------------------------------------
bpftool/1745 is trying to acquire lock:
ffff888131b85038 (&dev->lock){+.+.}-{4:4}, at: xdp_features_set_redirect_target+0x1f/0x80
but task is already holding lock:
ffff888131b85038 (&dev->lock){+.+.}-{4:4}, at: do_setlink.constprop.0+0x24e/0x35d0
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&dev->lock);
lock(&dev->lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by bpftool/1745:
#0: ffffffffa56131c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_setlink+0x1fe/0x570
#1: ffffffffaafa75a0 (&net->rtnl_mutex){+.+.}-{4:4}, at: rtnl_setlink+0x236/0x570
#2: ffff888131b85038 (&dev->lock){+.+.}-{4:4}, at: do_setlink.constprop.0+0x24e/0x35d0
stack backtrace:
CPU: 1 UID: 0 PID: 1745 Comm: bpftool Not tainted 6.15.0-rc6+ #1 PREEMPT(undef)
Hardware name: ASUS System Product Name/PRIME Z690-P D4, BIOS 0603 11/01/2021
Call Trace:
<TASK>
dump_stack_lvl+0x7a/0xd0
print_deadlock_bug+0x294/0x3d0
__lock_acquire+0x153b/0x28f0
lock_acquire+0x184/0x340
? xdp_features_set_redirect_target+0x1f/0x80
__mutex_lock+0x1ac/0x18a0
? xdp_features_set_redirect_target+0x1f/0x80
? xdp_features_set_redirect_target+0x1f/0x80
? __pfx_bnxt_rx_page_skb+0x10/0x10 [bnxt_en
? __pfx___mutex_lock+0x10/0x10
? __pfx_netdev_update_features+0x10/0x10
? bnxt_set_rx_skb_mode+0x284/0x540 [bnxt_en
? __pfx_bnxt_set_rx_skb_mode+0x10/0x10 [bnxt_en
? xdp_features_set_redirect_target+0x1f/0x80
xdp_features_set_redirect_target+0x1f/0x80
bnxt_xdp+0x34e/0x730 [bnxt_en 11cbcce8fa11cff1dddd7ef358d6219e4ca9add3]
dev_xdp_install+0x3f4/0x830
? __pfx_bnxt_xdp+0x10/0x10 [bnxt_en 11cbcce8fa11cff1dddd7ef358d6219e4ca9add3]
? __pfx_dev_xdp_install+0x10/0x10
dev_xdp_attach+0x560/0xf70
dev_change_xdp_fd+0x22d/0x280
do_setlink.constprop.0+0x2989/0x35d0
? __pfx_do_setlink.constprop.0+0x10/0x10
? lock_acquire+0x184/0x340
? find_held_lock+0x32/0x90
? rtnl_setlink+0x236/0x570
? rcu_is_watching+0x11/0xb0
? trace_contention_end+0xdc/0x120
? __mutex_lock+0x946/0x18a0
? __pfx___mutex_lock+0x10/0x10
? __lock_acquire+0xa95/0x28f0
? rcu_is_watching+0x11/0xb0
? rcu_is_watching+0x11/0xb0
? cap_capable+0x172/0x350
rtnl_setlink+0x2cd/0x570
Fixes: 03df156dd3 ("xdp: double protect netdev->xdp_flags with netdev->lock")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20250520071155.2462843-1-ap420073@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
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